1. Technical Field
This invention relates to telecommunications systems, and in particular to the provision of dedicated connections between defined points.
Modern telecommunications systems allow almost any telecommunications device to be connected to any other using conventional switched networks (circuit switched or packet switched).
2. Related Art
Early attempts to integrate voice and data systems relied on carrying digital data over a circuit-switched system initially designed for analogue signals, in particular voice. Conversely, modern packet-switched telecommunications systems, such as those running under the “Internet Protocol”, are configured for digital data, and analogue data, notably voice, has to be adapted to fit the protocol. Voice, in particular, has rather different requirements from those of data. Small values of latency (delay) are much more significant to a human listener than they are to a machine processing incoming data. Jitter—the variability of the delay—is even more significant. Conversely, the amount of redundancy in human speech is such that a human listener can still comprehend a voice signal that has suffered impairment to a much greater degree than would be acceptable in a data signal.
Existing “Voice over Internet Protocol” systems have procedures in place to reflect these different priorities, but call quality can still fall below that expected on a switched circuit, in particular because in a packet-switched system, unlike a conventional circuit-switched call, resources are shared and the underlying connection requirements are “best effort”. Contention for resources, for example between a number of simultaneous voice calls, can result in insufficient bandwidth being available to support the call traffic required. In comparison, provided a line is available, a circuit-switched system dedicates capacity dedicated solely to a single connection for the duration it is required.
The problems of latency and of contention with other subscribers for bandwidth, mean that dedicated point-to-point links are still preferred for certain applications. Such dedicated point-to-point physical circuits are expensive to provide as they require dedicated infrastructure to be installed over the entire length of the link, and there are few synergies available to reduce the cost of installing several such links. They are also less robust to system failure, and replacement or diversion (whether in an emergency or otherwise) requires major re-installation work.
The present invention addresses these issues by providing a method of creating virtual dedicated connections between parties to a packet switched system by populating a session parameter database with parameters for permitted sessions, and controlling access to a packet switched call routing system such that, when a session request is set up between a first party and a second party, the session is connected only if specified parameters of the requested session, including the identities of the first party and the second party, have previously been stored in the session parameter database.